Photomultiplier tube tightly arranged with substantially no space between adjacent tubes

Abstract

A photomultiplier tube unit including photomultiplier tubes densely assembled and thereby having an improved light sensing efficiency. The outer surfaces ( 2 b) of metal side tubes ( 2 ) of photomultiplier tubes ( 1 ) are in facial contact with one another, and thereby a high-density arrangement of photomultiplier tubes ( 1 ) are achieved. The side tubes ( 2 ) can be electrically connected to one another, and therefore the side tubes ( 2 ) can be easily made equipotential. As a result, it is unnecessary to electrically connect the stem pin ( 10 ) to the side tube ( 2 ) of each photomultiplier tube ( 1 ), facilitating the assembling of the photomultiplier tube unit. When a required photomultiplier tube ( 1 ) in a device (e.g., a gamma camera) having thus-united multiple photomultiplier tubes is replaced with a new one, the troublesome work of replacing photomultiplier tubes one by one is obviated, simplifying the replacement work.

What is claimed is:  
     
       1. A photomultiplier tube unit comprising: 
       a plurality of photomultiplier tubes that are juxtaposed, each of the plurality of photomultiplier tube including:  
       a faceplate;  
       a photocathode for emitting electrons in response to light incident on the faceplate;  
       an airtight vessel;  
       an electron multiplying section, disposed inside the airtight vessel, for multiplying the electrons emitted from the photocathode; and  
       an anode for outputting an output signal based on the electrons multiplied by the electron multiplying section,  
       wherein the airtight vessel comprises:  
       a metal stem plate for fixedly supporting the electron multiplying section and the anode with stem pins; and  
       a metal side tube with the stem plate fixed on one open end, and enclosing the electron multiplying section and the anode;  
       wherein the faceplate is fixed on the other open end of the metal side tube,  
       and wherein a plurality of airtight vessels are juxtaposed and outer surfaces of the plurality of airtight vessels are flat and in facial contact with one another, each outer surface being perpendicular in entirety to the corresponding photocathode.  
     
     
       2. The photomultiplier tube unit according to  claim 1 , wherein the plurality of airtight vessels are arranged and fixed on a single substrate. 
     
     
       3. The photomultiplier tube unit according to  claim 2 , wherein the substrate is formed with a plurality of pin holes for allowing the stem pins to be inserted therein. 
     
     
       4. The photomultiplier tube unit according to  claim 2 , wherein the substrate is provided with a plurality of socket pins having an upper portion formed with a concave portion for allowing the stem pin to be inserted therein. 
     
     
       5. The photomultiplier tube unit according to  claim 1 , wherein the outer surfaces of the side tubes are in facial contact with one another via an electrically conductive adhesive. 
     
     
       6. The photomultiplier tube unit according to  claim 1 , wherein the stem plate and the one end of the metal side tube are welded by a laser beam. 
     
     
       7. The photomultiplier tube unit according to  claim 1 , wherein the stem plate and the one end of the metal side tube are welded by an electron beam. 
     
     
       8. A radiation detector comprising: 
       a scintillator for emitting fluorescent light in response to radiation generated from an object of analysis;  
       a plurality of photomultiplier tubes for outputting electric charges based on fluorescent light emitted from the scintillator, and a position calculating section for performing calculations on the electric charges output from the plurality of photomultiplier tubes and outputting positioning signals of radiation issued from the object of analysis,  
       wherein each of the plurality of the photomultiplier tubes comprises:  
       a faceplate disposed in opposition to the scintillator;  
       a photocathode for emitting electrons in response to light incident on the faceplate;  
       an airtight vessel;  
       an electron multiplying section, disposed inside the airtight vessel, for multiplying the electrons emitted from the photocathode; and  
       an anode for outputting an output signal based on the electrons multiplied by the electron multiplying section,  
       wherein the airtight vessel comprises:  
       a metal stem plate for fixedly supporting the electron multiplying section and the anode with stem pins; and  
       a metal side tube with the stem plate fixed on one open end, and enclosing the electron multiplying section and the anode;  
       wherein the faceplate is fixed on the other open end of the metal side tube,  
       and wherein the radiation detector includes a photomultiplier tube unit in which a plurality of airtight vessels are juxtaposed, and outer surfaces of the plurality of airtight vessels are flat and in facial contact with one another, each outer surface being perpendicular in entirety to the corresponding photocathode.  
     
     
       9. The radiation detector according to  claim 5 , wherein the plurality of airtight vessels of the photomultiplier tube unit are arranged and fixed on a single substrate.